MCP655 impeller housing - Overlooked Mixed Metal

[Arcygenical]

EDIT: The metal is supposedly Stainless Steel alloy 316... According to a MUCH better spec sheet than the one I was previously using.

Now, the galvanic difference in potential between 316 and any of the popular copper alloys is quite similar to that between said Copper alloys and aluminum...


Postscript:
After running straight distilled + biocide for the last 6 months, the inside of the pump has suffered a bit of corrosion. The metal is discolored a dark black (that can't be removed, not even with an acid etch solution) and has started pitting a tiny bit.

And for clarification, I'm borrowing this from Skinee's lab's, a picture of the impeller housing - clearly a metal of some sort - one that's not copper.

At this point, I would not recommend going distilled only...Discussion definitely welcome.

 

[Imitation]

Hmm, that's interesting. I've had my setup running for over a year with distilled plus pentosin G11. Seems to be doing ok, temps have stayed steady. But if I ever do end up with problems i'll take a look at the pump.

 

[BillParrish]

http://www.pentosin.de/shop_produkt.php?c=214,231&pid=708

Pentosin Long-time Antifreeze does not affect sealings and features a good corrosion protection for all material used in cooler devices and non ferrous metals.

Bold is mine.

A biocide typically has no corrosion protection, its a bug killer only.

An interesting problem would be to determine the minimum concentration needed for corrosion protection as most % recommendations are based on the anit-freeze (temp) requirements. In other words, based on manuf data, the stainless steel and hard copper, assuming distilled water, what is the minimum concentration that would provide adequate (lets define it as no visible surface pitting ) protection for 5 years. Refreshing or changing the fluid allowed.

 

[psyshack]

What does the impeller look like? Any feathering of the vains on the outer edges or in the eye?

Mine still looks brand new with distilled water and about 3 oz of Honda car water coolant in it.

 

[Arcygenical]

The point of the thread is mainly to discuss with the Biocide + Distilled water only crowd.

Psyshack, your car water coolant is most likely an anticorrosive, and as bill said, Pentosin is a great anticorrosive.

I'm talking about the "I only use a silver killcoil and water" type loops

 

[psyshack]

The point of the thread is mainly to discuss with the Biocide + Distilled water only crowd.

Psyshack, your car water coolant is most likely an anticorrosive, and as bill said, Pentosin is a great anticorrosive.

I'm talking about the "I only use a silver killcoil and water" type loops

I understand the so called point of the thread. I was just wondering if there was any wear at all in the impeller or volute for that matter. There can be other issues that cause discoloring in a pump and pitting.

I will be rep'ing the Laing line in a few months as soon as Laing, ITT and B&G get the details all hammered out.

Moving On.

 

[AVT]

Well, I am glad I went with the DDC instead. Distilled+KillCoils loop here.